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Re: Making an X-10 lamp module immune to dimming



"isw" <isw@xxxxxxxxxxx> wrote in message
news:isw-988B8E.10385606062008@xxxxxxxxxxxxxxxxxxxxxxxxx

<stuff snipped>

> > > A while back, I hacked around in those controllers. Here are some of
my
> > > notes:
> > >
> > > "The IC generates a series of pulses, with at least one always
present,
> > > near but before the zero-crossing (i.e. even at "off" the triac is
> > > triggered, just very late in the half-cycle).
> > >
> > > "As the "brighten" signal is sent, the pulse first slides earlier in
the
> > > half-cycle, and then multiple pulses appear, with more and more as
full
> > > on is approached."
> >
> > Does that mean that the pulse width does not vary, but that the level of
the
> > light is determined by how many pulses of a fixed width are received
during
> > an AC cycle?
>
> The level of light is determined by when the leading edge of the
> earliest pulse arrives. The other pulses have no effect.

Would another way to say that be the light level is determined by the point
on the sine wave where the gate pulse arrives and that that unit stays on
until the end of the cycle, no matter what happens afterward in that cycle?
So it's not possible to have a sine wave that has four "bands" of on/off
pulses?  Or is it just that way for the X-10 modules?  I thought, when you
talked about pulses, that each one of them turned on the triac for a tiny
bit of time, and that all of them added together in each cycle increased the
power output.  That would require switch the triac on and off multiple times
within the cycle.  That description is true of how all the chopped A/C
cycles add up, but I think you're saying the pulses that follow are not
having any effect on the state of the triac.

After reading more, what I envision now from your description is a sliding
window sort of thing where the amount of current flowing depends on how far
you slide the ON window to the left-most window stop, which in this case, is
the zero crossing.  That sound anywhere near right?

> > I assume that would me they are obviously much shorter in
> > duration than 1/2 the AC cycle.  It sounds like they are "rechopping"
the
> > pulse into smaller pulses and that they aggregate to give the desired
end
> > level.  I am not explaining that well, I fear.   It seems like there are
two
> > pulse aggregations, a wheel within a wheel Ixion sort of thing.
>
> The fact that there is a train of pulses is probably an artifact of the
> way the IC in the X-10 unit accomplishes phase delay (to retard the
> timing of the gate drive).

So it might even be possible it's really just noise with no particular
function but no particular harm to the operation of the module.  I assume
you detected it with some sort of logic analyzer?

> > > What I wanted was a single duration-modulated pulse (wider for
brighter,
> > > of course), and here's how I got it:
> >
> > Why did you want to do this?  What is the benefit of going to pulse
width
> > from their system of number of pulses per cycle?>
>
> I was interested in using X-10 units to remotely control stuff other
> than lamps and coffee pots. Getting an optically isolated variable width
> pulse was a good starting place. I was not going to use that signal to
> drive a triac in amy way.

Sounds interesting.  Wouldn't such an extension give you trouble with
standard repeaters?

> > > 1) Add a signal diode (1N4148) in series with the signal from IC pin 6
> > > (i.e. cut the trace and hook it between the two points "B" on the
> > > schematic, cathode towards the transistor)
> >
> > Bear with someone with no experience but at least a little interest in
the
> > subject.  That's a high speed switching diode, AFAICT, and used in
series it
> > will pass current in only one direction . . .
>
> Yup. It allows the pulses from the IC to pass into a capacitor (for
> filtering them to an average DC level), while preventing the internals
> of the IC from (possibly) drawing a current that would prevent taht
> filtering from taking place.

So with the capacitor, the signal is being smoothed out from a pulse train
to voltage level.  Usenet II is going to need a whiteboard.  At least ten
times now I've wanted to show something with a simple sketch.   What does
that pulse train look like?  Is it a square wave with the lowermost part at
0 volts and the uppermost part at Vcc+ (not sure if that the right term).
Would the resulting DC level be Vcc+/2 or something close to that?

> > > 2) Change the 2.2 k resistor to 12 k.
> >
> > You would normally change a resistor value to change a time value in a
> > dependent RC circuit or to protect some other component from drawing too
> > much current, correct?
>
> Yup. In this case, I raised the value to allow a smaller capacitor to be
> used to get the time constant I wanted.

At least I remember that much from reading my 555 cookbook 20+ years ago.

> > > 3) Connect a 0.1 mfd. capacitor (ceramic is fine) from the cathode of
> > > the diode to V-
>
> That's the cap that integrates the pulse train into a DC value

You said "average DC level" before.  Is it safe to assume that DC value is
still going to show some trace of the underlying pulses because of how it
has been generated?  Is that called ripple or is that something else
entirely?

> > > 4) Change the 330 ohm resistor to 2.2 k
>
> Simplistically, the 12K resistor determines how fast the cap charges
> (but not discharges, because the diode prevents that), while the 2.2K
> controls the discharge time.

Is that capacitor discharging during the time the pulse is at zero, thus
providing current in the circuit where there would have been none without
it?


> --snip--
>
> > I've already discovered that X-10 gear has naked 110VAC running all over
the
> > circuit boards, making tinkering by noobs like me a lot more dicey than
> > trying to solder remote contacts to a coin cell powered keychain
controller
> > circuit board.
>
> True, but if you're careful to make sure it's not plugged in while you
> have your fingers in it, there's not much to worry about. There are no
> components in there that can store large chunks of energy, for example.

I learned that lesson with an 555 design that reversed an agitator motor by
charging up a fairly large capacitor.  They bite.

> Keep on hacking; that's the way to get better and more confident at it.

Thanks for the encouragement and the input.  I feel a little like I felt on
the first day of kindergarten when I saw all the sixth graders writing in
cursive, reading big books and most impressive of all, taking the stairs two
at a time!

I suppose this means I'll have to finally break down and open an account at
Digikey or Mouser.  (=;

--
Bobby G.





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